This application is directed to an apparatus for reducing flow through a housing to a significantly different rate or velocity than a flow exterior to the housing. The invention finds particular application in allowing passage of migrating fish, for example, under bridges, through road culverts, etc., where a waterway is confined to a confined region; however, the application will find use in related environments and applications.
It is not uncommon for a waterway or stream to be confined to a localized region where it passes beneath a bridge, through a road culvert, etc. During periods of heavy rainfall, for example, there is an attendant increase in the amount of water that flows through such regions, and the velocity in the waterway likewise increases. It is believed that fish have a tendency to migrate during such events. When encountering a narrow region during an increased flow event, the velocity or flow rate reaches a level that makes it difficult for the fish to pass through and the fish tend to cease their migration at these regions and these high flow events/regions become choke points.
Known structures are useful at channeling water through a confined region in order to provide protection to the road, bridge, or the like. Unfortunately, this only exacerbates the ability of fish to migrate through these regions. Thus, present arrangements simply do not provide a passage or region that is effective to reduce the velocity and allow the fish to more easily migrate therethrough, irrespective of the increased flow velocity in the stream or culvert.
Thus, a need exists for a passage, also referred to herein as a bio-passage, that improves migration for fish, and/or, reduces the flow in one region of the waterway generally irrespective of the flow external to that region, i.e., uninfluenced by external flow.